DESCRIPTION: Severe early childhood caries negatively affects the survival of the primary and permanent dentitions. Furthermore, the disease can markedly impair child development. There are limitations in methods that have been used to evaluate the microbiota that is responsible for severe early childhood caries (S-ECC). In particular, bacteria that evade routine culture, or have been uncultivable, have been overlooked. The long-term goal of the application is to better understand the pathogenesis of dental caries. The objective of this application is to identify the microbial pathogens of early childhood caries. The central hypothesis is that severe and recurrent early childhood caries is caused by a specific sub-set of bacterial species that are strong acid producers. The rationale for the application is that it will provide a comprehensive set of species that can be evaluated for their association with recurrent disease, and, in future studies, for their ability to predict caries, and as target species in the development of prophylaxis and treatment for this infection. The microbiota of diseased and healthy children will be identified and compared. The central hypothesis will be tested with two Specific Aims: 1) Identify candidate bacterial pathogens for severe early childhood caries. The working hypothesis is that the microbiota of S-ECC is enriched for disease-associated species compared to caries-free children. 2) Identify candidate bacterial pathogens for recurrent early childhood caries. The working hypothesis is that the microbiota of recurrent caries in children treated for severe caries is enriched for cariogenic pathogens compared with the microbiota of caries-free children, and S-ECC children not showing caries recurrence post-therapy. The innovative approach will combine cloning and sequencing bacterial 16S rRNA genes amplified from DNA with cultural methods to enrich for, and test acid producing ability of isolates. At the conclusion of the proposed research, it is expected that new cariogenic pathogens will be identified, and a microbiological profile that will be predictive of the potential for severe disease. The proposed research is significant because it is expected to provide tools to substantially improve our ability to predict the development of severe and recurrent early childhood caries, and indicate which species need suppression for effective therapy. As a result, it is expected that many of the negative consequences of this disease will be avoided, with attendant reductions in the costs of dental and related medical care.